1. Field of the Invention
The present invention relates generally to a compressing apparatus, and more particularly, to an apparatus for compressing, pumping, and discharging fluid by using a reciprocal linear movement of a piston.
2. Description of the Related Art
One typical example of a conventional apparatus for compressing fluid is shown in FIGS. 1 and 2.
FIGS. 1 and 2 are views schematically showing in cross-section, the structure and operation of a conventional apparatus for compressing fluid. The reference numeral 10 indicates a cylinder block, 20 indicates a piston, 30 indicates a valve plate, and 40 indicates a cylinder head.
As shown in FIGS. 1 and 2, the cylinder block 10 has a cylinder bore 11 with a predetermined diameter penetrating thereof in a lengthwise or longitudinal direction. The piston 20 is disposed within the cylinder bore 11 of the cylinder block 10 in order to move reciprocally therein.
The valve plate 30 is disposed adjacent the cylinder block 10. The valve plate 30 has a fluid suction hole 31 and a fluid discharge hole 32 disposed therein. In addition, the valve plate 30 has a suction valve 33 (most clearly shown in phantom in FIG. 2) and a discharge valve 34 (most clearly shown in FIG. 1) disposed thereon for opening and closing the fluid suction hole 31 and the fluid discharge hole 32, respectively.
Furthermore, the cylinder head 40 is disposed at the cylinder block 10 at a side where the valve plate 30 is disposed, and has a fluid suction chamber 41 and a fluid discharge chamber 42 disposed thereon. The fluid suction chamber 41 and the fluid discharge chamber 42 are each associated with the fluid suction hole 31 and the fluid discharge hole 32, respectively, of the valve plate 30. Moreover, a fluid suction manifold 43 and a fluid discharge manifold 44, which communicate with the fluid suction chamber 41 and the fluid discharge chamber 42, respectively, are connected with the cylinder head 40.
In the conventional apparatus for compressing the fluid having the above structure, a fluid is drawn, compressed, and discharged by the piston 20 reciprocally moving within cylinder bore 11 by receiving power provided from a piston driving source (not shown). The piston 20 moves in the cylinder bore 11 of the cylinder block 10.
More specifically, when the piston 20 moves from a top dead point T (FIG. 1) of the cylinder bore 11 to a bottom dead point B (FIG. 2) of the cylinder bore 11, the suction valve 33 opens the suction hole 31 of the valve plate 30 as a result of a difference in pressure between the inside of the cylinder bore 11 and the inside of fluid suction chamber 41, as shown in FIG. 2. Therefore, the fluid is drawn into the inside of the cylinder bore 11 of the cylinder block 10 through the suction manifold 43, the suction chamber 41 of the cylinder head 40, and the suction hole 31 of the valve plate 30. The pressure in the discharge chamber 42 of the cylinder head 40 is higher than that of the inside of the cylinder bore 11, thus the discharge valve 34 is retained in a closed position (as shown in FIG. 2), thus closing off the discharge hole 32.
On the other hand, when the piston 20 moves from the bottom dead point B (FIG. 2) of the cylinder bore 11 to the top dead point T (FIG. 1) of the cylinder bore 11, then the fluid, drawn into the cylinder bore 11 during the piston downstroke, is gradually compressed. Finally, as shown in FIG. 1, when the piston 20 reaches the top dead point T, the pressure in the cylinder bore 11 becomes higher than that of the discharge chamber 42 of the cylinder head 40, thus the discharge valve 34 opens the discharge hole 32 of the valve plate 30. Accordingly, the compressed fluid is discharged through the discharge hole 32 of the valve plate 30, into the discharge chamber 42 of the cylinder head 40, and out through the discharge manifold 44. At this time, the pressure of the suction chamber 41 of the cylinder head 40 is lower than that of the cylinder bore 11, thus the suction valve 33 is retained in a closed position (as shown in FIG. 1), thus closing off the suction hole 32.
Furthermore, when the piston 20 moves again to the bottom dead point B, the suction hole 31 is opened by the suction valve 33, and the discharge hole 32 is closed by the discharge valve 34, thus causing fluid to be drawn from the suction chamber 41. After that, when the piston 20 moves again to the top dead point T, the drawn fluid is repeatedly compressed and discharged, in a continuously operating cycle.
However, in the conventional apparatus for compressing the fluid as described so far, the fluid compressed by the piston 20 is not fully discharged. Some of the compressed fluid is left in the discharge hole 32 of the valve plate 30, Therefore, while the fluid is being drawn, in other words, when the piston 20 moves from the top dead end point T to the bottom dead end point B, the remaining fluid, at a high pressure, is re-expanded as the piston 20 moves in its downstroke. Owing to the re-expanded high pressure fluid, in the beginning of the fluid drawing sequence, in other words, when the piston 20 moves to the bottom dead end point B, the pressure of the cylinder bore 11 is lower than that of the discharge chamber 42 of the cylinder head 40, but the pressure is higher than that of the suction chamber 41. Therefore, at the time when the piston 20 starts its downstroke, moving to the bottom dead end point B, suction does not immediately occur. Yet, after the pressure of the cylinder bore 11 becomes lower than that of the suction chamber 41, as the piston 20 fully moves to the bottom dead end point B, the suction valve 33 is opened and new fluid is drawn. Consequently, in the conventional apparatus for compressing the fluid, as the high pressure fluid remaining in the suction hole 32 creates a clearance volume of the cylinder bore 11 during every stroke cycle, the amount of the fluid drawn into cylinder bore 11 is decreased and results in a deterioration in efficiency.
Moreover, since the conventional apparatus for compressing the fluid must employ the suction valve 33 and the discharge valve 34 having a complex structure for opening the suction hole 31 and the discharge hole 32, assembly of the compressor apparatus is complicated. Furthermore, it does not lend itself to a good production method and also the construction results in high production costs.
An object of the present invention is to provide an apparatus for compressing fluid capable of improving efficiency by removing the clearance volume found in a conventional cylinder bore as compressed fluid is fully discharged.
Another object of the present invention is to provide an apparatus for compressing fluid capable of reducing the production cost and improving the ease of assembly and the manufacturing productivity as the compressing apparatus is constructed, by providing a piston that opens and closes a fluid suction port without having a separate suction valve device and by providing a discharge valve assembly having a simple structure.
The above objects are accomplished by providing an apparatus for compressing a fluid comprising: a cylinder block including a cylinder bore with a predetermined diameter penetrating the cylinder block in a lengthwise direction, at least one fluid suction port penetrating in an intersecting direction with the cylinder bore, and at least a pair of fluid discharge ports, each discharge port having a slot shape with one opening formed at an end portion of the cylinder bore; a piston for reciprocally moving in the cylinder bore of the cylinder block; a discharge valve assembly movably disposed at the cylinder bore in order to selectively open and close the fluid discharge ports of the cylinder block, the discharge valve assembly including a valve piston having a flange for limiting a movement of the discharge valve assembly; and a cylinder head for forming a discharge chamber communicated with the fluid discharge ports of the cylinder block by being connected with the cylinder block, and the cylinder head having a fluid discharge passage of the discharge chamber.
According to the above described apparatus for compressing fluid, the fluid is drawn as the fluid suction port is selectively opened and closed by the piston reciprocally moving in the cylinder bore of the cylinder block. In addition, the fluid is discharged through the fluid discharge port opened by the valve piston moved by the increased fluid pressure in the cylinder bore. Therefore, as the conventional suction valve with a complex structure is removed, and the structure of the discharge valve becomes simpler, assembly and productivity of the compressing apparatus will be improved. Moreover, the production cost will be also reduced remarkably. Furthermore, since the high pressure fluid compressed in the cylinder bore is fully discharged through the discharge port, the clearance volume generated due to remaining fluid in the cylinder bore can be eliminated, and thus compressing efficiency will be improved.
According to the preferred embodiment of the present invention, in the apparatus for compressing fluid, the position of the top dead endpoint of the piston arranged at a point slightly past an end portion of the cylinder bore, and accordingly, any fluid compressed in the cylinder bore is fully discharged as the piston and the valve piston come into contact with each other at the top dead end point.
Furthermore, the fluid suction port is disposed immediately before a bottom dead end point, that is, the most retreated position of the piston, and accordingly, the fluid is promptly drawn by the vacuum developed in the cylinder bore as the fluid suction port is suddenly opened when the piston reaches the bottom dead end point.
The discharge valve assembly preferably comprises: a valve piston for moving in the cylinder bore, the valve piston having a flange for limiting the movement of the valve piston by being in contact with an end wall of the cylinder bore, the flange having a first boss formed roughly in a center of a flange; a support plate disposed in the cylinder head being distanced for a predetermined space with the valve piston, the support plate has a second boss formed therein corresponding to the first boss and a plurality of fluid passages radially formed centering the second boss; and an resilient member disposed between the valve piston and the support plate, the resilient member for elastically supporting the valve piston to be moved in a direction that the valve piston closes the fluid discharge ports.
In addition, the cylinder block can be formed to have either a circular appearance or a square appearance.
The fluid suction ports can be disposed at two opposite sides of the cylinder block, or more than two fluid suction ports can be disposed extending through the cylinder block at predetermined intervals.
The fluid suction ports can be tapered or formed as a two layered port having one port of greater diameter and a second port of smaller diameter, or alternatively, a port compounded with these two types.
Moreover, the fluid suction ports can be formed to have a more extended suction area by cutting away a portion of at least one side of the cylinder block. In this case, as the area of the fluid suction ports becomes greater, the fluid can be drawn into the cylinder bore 11 more efficiently.